Coordinate measuring devices are available today in a variety of designs and degrees of automation. Besides CNC controlled devices, which carry out complex measuring programs under automatic control on the most varied workpieces, so-called manual, i.e., unmotorized or only partially motorized, coordinate measuring devices are also in use. In these devices, the operator guides the probe by hand on the locations of the workpiece to be measured.
The last-mentioned devices are mostly air cushion mounted and the moving masses to be guided are minimized as far as possible by a corresponding construction design. The operator nevertheless has to exert considerable forces at times to accelerate and decelerate the measuring slide of the machine in order to overcome inertia. If these forces are introduced in the neighborhood of the probe, a deformation of the machine coordinate system results. This results in measurement errors, which are often large. If, for example, rigid probes are used for the purpose of shape testing in such manually guided coordinate measuring devices, and the probe is caused to travel continuously along a geometrical element, e.g., a surface or the inner wall of a bore, with continuous measurement point transfer, very many measurement points can be sensed very rapidly, without great cost, and very elegantly (e.g., 1,000 points in a bore of 50 mm diameter in 2-3 seconds). However, because of the above-mentioned reaction forces, measurement errors of between 10 .mu.m and 100 .mu.m arise, depending on the skill of the operator and the stiffness of the probe.
Attempts have been made to eliminate these errors by having the machine guided, as far as possible, not on the measuring arm or sleeve, but on the cross slide carrying it. However, the arm or sleeve then has to be either motorized or operated with both hands.
The per se very elegant process of surveying the workpiece geometry by scanning with a rigid probe is therefore used today on manually guided coordinate measuring devices only in the measurement of plane curves with low requirements for accuracy.
A coordinate measuring device is described in British Patent 1,498,009. Its probe is mounted, for motion in several spatial directions, on rotation shafts arranged one behind the other. This device involves relative difficulty and entails substantial cost if geometric elements such as bores and surfaces are to be scanned that have their axes of symmetry lying at an angle to the two vertically upright rotation shafts of the device.